电气自动化专业英语.ppt

Chapter 1 Electric and Electronic Technology Fundamentals,Unit 3 Transistor,Text,New Words and Expressions,Exercises,End,Process of Translation,Unit3 Transistor,A transistor is a semiconductor device used to amplify and switch electronic signals. It is made of a solid piece of semiconductor material, with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistors terminals changes the current flowing through another pair of terminals. Because the controlled (output) power can be much more than the controlling (input) power, the transistor provides amplification of a signal. Today, some transistors are packaged individually, but many more are found embedded in integrated circuits.,The transistor is the fundamental building block of modern electronic devices, and is ubiquitous in modern electronic systems. Following its release in the early 1950s the transistor revolutionised the field of electronics, and paved the way for smaller and cheaper radios, calculators, and computers, amongst other things.,Unit3 Transistor,Importance The transistor is the key active component in practically all modern electronics, and is considered by many to be one of the greatest inventions of the twentieth century. Its importance in todays society rests on its ability to be mass produced using a highly automated process (semiconductor device fabrication) that achieves astonishingly low per- transistor costs.,Unit3 Transistor,Unit3 Transistor,Although several companies each produce over a billion individually packaged (known as discrete) transistors every year, the vast majority of transistors now produced are in integrated circuits (often shortened to IC, microchips or simply chips), along with diodes, resistors, capacitors and other electronic components, to produce complete electronic circuits. A logic gate consists of up to about twenty transistors whereas an advanced microprocessor, as of 2009, can use as many as 2.3 billion transistors (MOSFETs). “About 60 million transistors were built this year 2002 . for each man, woman, and child on Earth.“,The transistors low cost, flexibility, and reliability have made it a ubiquitous device. Transistorized mechatronic circuits have replaced electromechanical devices in controlling appliances and machinery. It is often easier and cheaper to use a standard microcontroller and write a computer program to carry out a control function than to design an equivalent mechanical control function.,Unit3 Transistor,Transistor as a switch Transistors are commonly used as electronic switches, for both high power applications including switched-mode power supplies and low power applications such as logic gates. In a grounded-emitter transistor circuit, such as the light-switch circuit shown, as the base voltage rises the base and collector current rise exponentially, and the collector voltage drops because of the collector load resistor. The relevant equations:,Unit3 Transistor,URC =ICERC, the voltage across the load (the lamp with resistance Rc) URC +UCE =UCC, the supply voltage shown as 6V If UCE could fall to 0 (perfect closed switch) then IC could go no higher than UCC/Rc , even with higher base voltage and current. The transistor is then said to be saturated. Hence, values of input voltage can be chosen such that the output is either completely off, or completely on. The transistor is acting as a switch, and this type of operation is common in digital circuits where only “on“ and “off“ values are relevant.,Unit3 Transistor,Unit3 Transistor,Transistor as an amplifier The common-emitter amplifier is designed so that a small change in voltage in (Vin) changes the small current through the base of the transistor and the transistors current amplification combined with the properties of the circuit mean that small swings in Uin produce large changes in Uout. Various configurations of single transistor amplifier are possible, with some providing current gain, some voltage gain, and some both. From mobile phones to televisions, vast numbers of products include amplifiers for sound reproduction, radio transmission, and signal processing. The first discrete,transistor audio amplifiers barely supplied a few hundred milliwatts, but power and audio fidelity gradually increased as better transistors became available and amplifier architecture evolved. Modern transistor audio amplifiers of up to a few hundred watts are common and relatively inexpensive.,Return,Unit3 Transistor,Unit3 Transistor,Types Transistors are categorized by Semiconductor material: germanium, silicon, gallium arsenide,silicon carbide, etc. Structure: BJT, JFET, IGFET (MOSFET), IGBT, “other types“ Polarity: NPN, PNP (BJTs); N-channel, P-channel (FETs) Maximum power rating: low, medium, high ; Maximum operating frequency: low, medium, high, radio frequency (RF), microwave (The maximum effective frequency of a transistor is denoted by the term fT, an abbreviation for “frequency of transition“. The frequency of transition is the frequency at which the transistor yields unity gain).,Unit3 Transistor,Application: switch, general purpose, audio, high voltage, super-beta, matched pair Physical packaging: through hole metal, through hole plastic, surface mount, ball grid array, power modules Amplification factor hfe (transistor beta) Thus, a particular transistor may be described as silicon, surface mount, BJT, NPN, low power, high frequency switch.,Unit3 Transistor,Packaging Through-hole transistors (tape measure marked in centimetres)Transistors come in many different packages (semiconductor packages) (see images). The two main categories are through-hole (or leaded), and surface-mount, also known as surface mount device (SMD). The ball grid array (BGA) is the latest surface mount package (currently only for large transistor arrays). It has solder “balls“ on the underside in place of leads. Because they are smaller and have shorter interconnections, SMDs have better high frequency characteristics but lower power rating.,Unit3 Transistor,Transistor packages are made of glass, metal, ceramic, or plastic. The package often dictates the power rating and frequency characteristics. Power transistors have larger packages that can be clamped to heat sinks for enhanced cooling. Additionally, most power transistors have the collector or drain physically connected to the metal can/metal plate. At the other extreme, some surface-mount microwave transistors are as small as grains of sand. Often a given transistor type is available in sundry packages. Transistor packages are mainly standardized, but the assignment of a transistors functions to the terminals is not: other transistor types can assign other functions to the packages terminals. Even for the same transistor type the terminal assignment can vary (normally indicated by a suffix letter to the part number, q.e. BC212L and BC212K).,New Words and Expressions,transistor n. 晶体管 amplify vt. 放大, 增强 ubiquitous adj. 普遍存在的 calculator n. 计算器 astonishingly adv. 令人吃惊地 discrete adj. 不连续的, 离散的 MOSFET 金属氧化物半导体场效应晶体管 flexibility n. 弹性, 适应性 mechatronic n. 机电一体化 electromechanical adj. 机电的 saturate v. 使饱和, 浸透, 使充满 milliwatt n. 毫瓦 gallium arsenide 砷化镓 silicon carbide 碳化硅 BJT 双极结型晶体管(Bipolar Junction Transistor) JFET 结晶型场效应晶体管(junction field effect transistor) IGFET 绝缘栅场效应晶体管(isolated-gate field effect transistor ) IGBT, 绝缘栅双极型晶体管(Insulated Gate Bipolar Transistor) N-channel n沟道 abbreviation n. 缩写, 缩写词 denote vt. 指示, 表示 yield v. 出产, 生产 super-beta 高倍放大 matched pair 推挽式放大 through hole 透眼, 透孔 surface mount 面封装式 ball grid array 球栅阵列(封装) power module 功率模块(封装) amplification factor 放大倍数 centimeter n. 厘米, 公分 package n. 包装，封装 ceramic n. 陶瓷 collector n. 集电极 drain n. 漏极 grain n. 谷粒, 细粒 sundry adj. 各式各样的 assignment n. 分配, 安排 suffix n. 后缀, 下标,Return,Process of Translation,理解阶段 主要是通过辨明词义，弄清各种语法成分及其相互关系，并把前后句子贯串起来理解，形成对原文的完整印象，真正掌握原文的内容和实质。,表达阶段 是在理解的基础上，以忠实于原意为前提，灵活地运用各种翻译方法和技巧，写出符合汉语规范、表达习惯以及翻译标准的译文。,校核阶段 是理解与表达的进一步深化，是对原文内容进一步核实，对译文语言进一步推敲，进行必要的润色和修改，使译文符合标准规范。,Exercises,I. Comprehension,1. Transistors are commonly used as electronic _, for both high power applications including swiched-mode power supplies and low power applications such as logic gates. A. heaters B. transformers C. amplifiers D. switches 2. This arrangement where the emitter (E) is in the controlling ci